There was a job offer. That it was for an unpaid position is irrelevant, since the law makes no distinction between a paying or non-paying job offer. The White House has admitted a specific job offer was made, via ABC News:
Last summer, Chief of Staff Rahm Emanuel asked former President Bill Clinton to talk to Sestak about appointment to a prestigious but unpaid presidential advisory board, White House counsel Bob Bauer revealed in a report out today.